Grade 9 Science Exam Review - Chemistry PDF

Grade 9 Science Exam Review Chemistry Terms to Review: Atom Electron Element Group (chemical) Ionic compound Matter Mechanical mixture Molecular compounds Neutron Period Proton Pure substance Solution...

Grade 9 Science Exam Review Chemistry Terms to Review: Atom Electron Element Group (chemical) Ionic compound Matter Mechanical mixture Molecular compounds Neutron Period Proton Pure substance Solution Suspension Key Concepts: 1. Identify the following as either a physical or chemical property: a. Diamonds are hard - physical b. Gallium will melt in the palm of your hand - physical c. Wood burns easily - chemical d. Iron is magnetic - physical e. Some cleaners are corrosive - chemical 2. Distinguish between the boiling and melting point: The boiling point is the temperature at which a liquid evaporates and turns into gas, whereas the melting point is the temperature at which a solid melts to become a liquid. For example, at the melting point of water, ice turns into liquid water; and at its boiling point, water evaporates and turns into water vapor. 3. Use the particle theory of matter to explain how a solid can melt if sufficiently heated?  Melting occurs when a solid is heated and turns to liquid. The particles in a solid gain enough energy to overcome the bonding forces holding them firmly in place. During melting, the particles start to move about, staying close to their neighbouring particles, then move more freely. 4. What is the difference between a group and a period in the periodic table? Periods are horizontal rows (across) the periodic table, while groups are vertical columns (down) the table. Atomic number increases as you move down a group or across a period. 5. How are metals, and non-metals organized in the periodic table? The metals are to the left of the line (except for hydrogen, which is a non-metal), the nonmetals are to the right of the line, and the elements immediately adjacent to the line are the metalloids. 6. Give the number of valence electrons in an atom of each of the following elements a. Hydrogen - 1 b. Aluminum - 3 c. Carbon - 4 d. Oxygen - 6 e. Chlorine - 7 7. Use the diagram below to answer the following questions: a. What is the element (ion) shown Calcium  b. What group in the periodic table does this element belong to? 2 (metals) c. How many valence electrons are in a neutral atom of this ion? 2 8. Explain what an “ion charge” is? Atoms carrying positive or negative charges are called ions. If an atom has gained one or more electrons, it is negatively charged and is called an anion. If an atom has lost one or more electrons, it is positively charged and is called a cation. 9. How can ion charges be used to determine the chemical formula of compounds? An alternative way to writing a correct formula for an ionic compound is to use the criss-cross method. In this method, the numerical value of each of the ion charges is crossed over to become the subscript of the other ion. 10. Is a metal element more likely to form an ion by losing electrons or by gaining them? Metals tend to lose electrons and form positively charged ions called cations. Non- metals tend to gain electrons and form negatively charged ions called anions. For example, sodium metal, Na, loses one electron to form the Na+ ion. 11. Give the name of the elements in the following compounds: a. LiCl – Lithium and chlorine (ionic) b. Al2S3 – Aluminium and sulphur (ionic) c. AgF – Silver and fluorine (ionic) d. ZnO – Zinc and oxygen (ionic) e. N2S3 – Nitrogen and sulphur (molecular) 12. Identify each of the substances in the previous question as an ionic compound or a molecular compound (answers above). Short Answers 13. Describe two patterns found in the periodic table? The specific patterns that can be seen in the periodic table are that the elements present in a group have a similar number of outer electrons, and rows are arranged from top to bottom and from left to right in increasing atomic number order. 14. Draw Bohr Diagrams Oxygen Sodium 1+ ION Magnesium 15. Write the chemical names of the following compounds: a. MgBr2 – Magnesium bromide b. Ba3N – Barium nitride c. Ca3P2 – Calcium phosphide d. Al2O3 – Aluminium oxide e. NaI – Sodium iodide f. CaCl2 – Calcium chloride g. K2CO3 – Potassium carbonate h. MgSO4 – Magnesium sulphate i. Cl2O5 – Dichlorine pentaoxide 16. Identify each of the following compounds as either ionic or molecular, and give the formula for each one:  a. Magnesium phosphide – Mg3P2 (ionic) b. Lithium nitride – Li3N (ionic) c. Phosphorus pentachloride – PCl5 (molecular) d. Aluminum bromide – AlBr3 (ionic) e. Calcium sulphide – CaS (ionic) f. Sulphur Dioxide – SO2 (molecular) g. Potassium iodide – KI (ionic) h. Sodium oxide – Na2O (ionic) i. Calcium hydroxide – Ca(OH)2 (ionic) j. Aluminum carbonate – Al2(CO3)3 (ionic) k. Nitrogen trichloride – NCl3 (molecular) 17. Fill out the following table: Symbol Name Atomic Protons in Neutrons in mass Atom Atom H Hydrogen 1.01 1 0 Cl Chlorine 35.34 17 18 Ca Calcium 40.08 20 20 Ag Silver 107.87 47 60 Ne Neon 20.18 10 10 U Uranium 238.03 92 146